Biaxially Oriented Polyester Film Coating for Humid Ink Adhesion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing polyester films with copolyester adhesion-promoting coatings suffer from poor adhesion to printing inks, especially under humid conditions, and often contain components that are not suitable for food contact applications, affecting economic viability and production efficiency.
Innovation Solution
A multilayer polyester film with a base layer composed of at least 70% thermoplastic polyester, containing specific copolyesters and silanes with vinyl or methacrylic functionalization, applied inline during production, ensuring strong adhesion to printing inks and resistance to moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If copolyester adhesion-promoting coating is applied to polyester film, then adhesion to printing inks is improved, but adhesion deteriorates under humid conditions
Solution Approach 1:
The patent uses a copolyester composition containing sulfonate group-bearing monomers combined with silane crosslinking agents to create a composite coating system. The copolyester provides adhesion promotion while the silane crosslinking creates a moisture-resistant network, resolving the contradiction between initial adhesion and humidity resistance.
Solution Approach 2:
The patent modifies the chemical parameters of the copolyester by incorporating sulfonate group-bearing monomers (5-SIPA) and controlling the glass transition temperature within specific ranges (20-80°C). These parameter changes enable the coating to maintain adhesion properties under varying humidity conditions while preserving ink adhesion.
2Strength
If epoxy crosslinkers are used to improve adhesion and solvent resistance, then coating performance is improved, but health risks and production costs increase
Solution Approach 1:
The patent replaces expensive and hazardous epoxy crosslinkers with silane-based crosslinking agents that are safer, more cost-effective, and suitable for food contact applications. The silane system provides comparable crosslinking functionality without the genotoxicity concerns of epoxy compounds.
Solution Approach 2:
The patent introduces silane crosslinking agents as an intermediary substance that mediates between the copolyester coating and the substrate, providing crosslinking functionality similar to epoxy but without the harmful effects. The silane forms a bridging network that maintains adhesion and solvent resistance while eliminating health risks.
3Strength
If copolyester coating is applied to improve adhesion, then coating performance is improved, but moisture sensitivity increases causing washing off
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating hydrophobic silane groups and controlling the copolyester structure with specific glass transition temperatures. These parameter changes reduce moisture sensitivity while maintaining adhesion strength, preventing the coating from being washed off.
Solution Approach 2:
The patent creates a composite coating system where copolyester provides adhesion promotion and silane crosslinking provides moisture resistance. The synergistic combination of these two materials resolves the contradiction between adhesion strength and moisture stability, preventing coating removal while maintaining substrate bonding.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The film exhibits excellent adhesion to UV printing inks, maintains mechanical strength, and is suitable for food contact applications, with improved economic efficiency and reduced production defects.
Implementation Method 1
at least one silane bearing vinyl (or methacrylic) groups... which are suspected of being genotoxic
Implementation Method 2
the crosslinking of sulfo-copolyesters with epoxides
Implementation Method 3
a copolyester-containing coating that adheres well to printing inks... and that also endures under humid conditions
Implementation Method 4
suitable for printing with various printing inks, in particular UV printing inks
Data Source
AI summary
The invention relates to a polyester film provided with a coating on at least one side, wherein the coating is the drying product of an aqueous dispersion comprising, in addition to water, at least one copolyester component and one silane component, wherein: • the copolyester component consists of a sulfonate-bearing monomer unit to a proportion of 3 to 35 mol% and is present in the dried coating to a proportion of 40-85 wt%, and • the silane component bears vinyl or methacrylic groups as well as alkoxy groups and is present in the dried coating to a proportion of 15-60 wt%. The invention further relates to a method for its production and its use.